U.S. patent application number 11/257854 was filed with the patent office on 2007-05-31 for bone fixation device and method.
This patent application is currently assigned to ROBERT J. MEDOFF. Invention is credited to Robert J. Medoff.
Application Number | 20070123880 11/257854 |
Document ID | / |
Family ID | 38088508 |
Filed Date | 2007-05-31 |
United States Patent
Application |
20070123880 |
Kind Code |
A1 |
Medoff; Robert J. |
May 31, 2007 |
Bone fixation device and method
Abstract
For fixation of an oblique fracture in a long bone, a fixation
plate is placed along the bone across the fracture and tabs
extending outwardly from the plate engage the bone at upper and
lower surfaces respectively of the proximal and distal fragments of
the bone. By applying compressive force to the bone by the tabs,
the fragments are subjected to compression force across the
fracture and to a torque which opposes bone shortening.
Inventors: |
Medoff; Robert J.; (Kailua,
HI) |
Correspondence
Address: |
LADAS & PARRY
26 WEST 61ST STREET
NEW YORK
NY
10023
US
|
Assignee: |
MEDOFF; ROBERT J.
TELLMAN; LARS G.
MEDOFF; DAVID
|
Family ID: |
38088508 |
Appl. No.: |
11/257854 |
Filed: |
October 25, 2005 |
Current U.S.
Class: |
606/326 |
Current CPC
Class: |
A61B 17/809 20130101;
A61B 17/8061 20130101; A61B 17/8085 20130101; A61B 17/8004
20130101 |
Class at
Publication: |
606/069 |
International
Class: |
A61F 2/30 20060101
A61F002/30 |
Claims
1. Apparatus for fixation of distal and proximal fragments of an
oblique fracture in a bone, said apparatus comprising: a fixation
plate having a first portion adapted for attachment to the distal
fragment and a second portion adapted for attachment to the
proximal fragment such that the plate extends across the oblique
fracture, said plate having means for engaging the bone to apply
force to the distal and proximal fragments in a direction extending
transversely of the bone to produce a compressive force across the
fracture.
2. Apparatus as claimed in claim 1, wherein said means compresses
at least one tab extending outwardly of said plate at a position
and length to engage one of said fragments to apply said transverse
force thereto.
3. Apparatus as claimed in claim 1, wherein said means comprises
first and second tabs extending outwardly of said plate, said first
tab being positioned and of sufficient length for engaging the
proximal fragment and said second tab being positioned and of
sufficient length for engaging the distal fragment, said first and
second tabs being spaced in a longitudinal direction of the plate
to provide a counter-rotational torque to oppose destabilizing
sliding of the fragments.
4. Apparatus as claimed in claim 3, wherein said first and second
tabs are positioned for engaging upper and lower surfaces of the
fragments, above and below the fracture on opposite sides of the
fracture.
5. Apparatus as claimed in claim 4, wherein said tabs are bendable
to engage the fragments and apply the compressive force against the
fragments.
6. Apparatus as claimed in claim 4, wherein said tabs are provided
with a stress relief for directing bending of the tabs at a
specific location
7. Apparatus of claim 6 in which stress relief is of the form of a
notch at the edge of the tab.
8. Apparatus as claimed in claim 4, wherein said tabs include
projections having teeth to bite into the respective fragments.
9. Apparatus as claimed in claim 8, wherein said teeth are located
at lower ends of the projections.
10. Apparatus as claimed in claim 8, wherein said tabs have holes
to facilitate bending the tabs with a bending tool.
11. Apparatus as claimed in claim 10, wherein said holes in the
tabs are threaded.
12. Apparatus as claimed in claim 3, wherein the fixation plate is
provided with holes for bone screws, said holes being located in
said first and second portions.
13. Apparatus as claimed in claim 12, wherein at least one of said
holes is oblong to allow sliding of the fixation plate along the
bone before the bone screw in the oblong hole is tightened.
14. Apparatus as claimed in claim 13, wherein said plate has a
longitudinal axis and said oblong hole is oblique with respect to
said longitudinal axis so that when the plate is longitudinally
displaced, the plate will undergo rotation and change the pressure
of the tabs against the fragments.
15. Apparatus as claimed in claim 1 wherein the fixation plate
extends in a longitudinal direction and is curved in the
longitudinal direction to conform with the bone.
16. Apparatus as claimed in claim 15, wherein in a transverse
direction the plate is shaped to conform with the bone.
17. Apparatus as claimed in claim 16, wherein the fixation plate is
shaped to conform to the lateral malleolus of an ankle.
18. Apparatus as claimed in claim 1 wherein the plate includes a
lip at a forward end of the first portion to engage a distal
surface of the distal fragment.
19. Apparatus as claimed in claim 3 comprising a pin connecting
said tabs together.
20. A fixation plate for fixation of oblique fractures of the
lateral malleolus of the ankle bone, said fixation plate comprising
an elongated body having a first portion for attachment to a distal
fragment of the oblique fracture of the lateral malleolus and a
second portion for attachment to a proximal fragment of the oblique
fracture of the lateral malleolus, the plate being of a length for
extending across the oblique fracture, and first and second tabs
extending in the same direction outwardly from the body, said tabs
being longitudinally spaced along said body, the first tab being
disposed at a lower edge of said first portion for engaging an
outer surface of the distal fragment and the second tab being
disposed at an upper edge of said second portion for engaging an
outer surface of the proximal fragment, said tabs being located on
opposite sides of the oblique fracture and above and below the
oblique fracture, the tabs being bendable for contact with the bone
on upper and lower surfaces thereof to produce compression of the
fragments against one another and provide a counter-resistant
torque to oppose displacement of the fragments causing shortening
of the bone.
21. The fixation plate as claimed in claim 20, wherein said tabs
have lower ends with pointed teeth for biting into the respective
fragments.
22. The fixation plate as claimed in claim 20, wherein the tabs
have holes to facilitate bending thereof.
23. The fixation plate as claimed in claim 20, wherein the plate is
shaped longitudinally and transversely to conform to the lateral
malleolus.
24. A method of fixation of an oblique fracture in a bone, said
method comprises the steps of: reducing the fracture by abutting
proximal and distal fragments along the oblique fracture applying a
fixation plate along the fractured bone and across the fracture
such that a first portion of the fixation plate is adjacent to the
distal fragment and a second portion of the fixation plate is
adjacent to the proximal fragment, providing tabs extending from
the first and second portions of the fixation plate at locations
spaced longitudinally of the plate and at positions at which one
tab faces an upper surface of the bone while another tab faces a
lower surface of the bone, and bringing the tabs into contact with
the upper and lower surfaces of the bone to apply force to the
distal and proximal fragments of the bone and produce compression
of distal and proximal fragments across the fracture.
25. The method as claimed in claim 24, wherein said tabs are
brought into contact with the bone by bending the tabs against the
bone.
26. The method as claimed in claim 25 comprising forcing said tabs
against the bone by rotating the fixation plate.
27. The method as claimed in claim 26 comprising securing the first
and second portions of the fixation plate to the bone fragments
while the fragments are compressed across the fracture.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a bone fixation device used for
fixation of two bone fragments or segments that have an oblique
surface of contact, such as the case with an oblique fracture of
the lateral malleolus of the ankle.
[0002] The invention further relates to a method of bone fixation
of such oblique fractures.
BACKGROUND AND PRIOR ART
[0003] Achieving stable fixation of two bone segments having an
oblique contact surface can be difficult. For example, external
rotation injuries of the ankle may often result in a short oblique
fracture of the lateral malleolus. Because of the oblique
orientation of the fracture line, simple apposition of the bone
surfaces is nearly always unstable, since axial loading forces on
the bone cause sliding of the two bone surfaces along the oblique
fracture line and contribute to potential problems of shortening,
non-union, and loss of reduction. For fractures involving the
lateral malleolus of the ankle, even as little as 1 millimeter of
shortening can lead to debilitating arthritis and ankle
instability.
[0004] In the case of an oblique fracture of the lateral malleolus,
the opposing bone ends of segments or fragments have the tendency
to slide in opposite directions and shorten since axial loading of
the bone produces shear stresses contributed by the obliquity of
the fracture surface. This will be explained with reference to FIG.
1. If a reference point C is considered at the exact center of the
fracture, axial forces F on the bone segments 1,2 produce sliding
of the segments along the oblique fracture in opposite directions.
The displacement of the two bone segments 1,2 in opposite
directions causes the axial forces F on either side of the fracture
to displace off center, resulting in the production of a force
couple or torque T that aggravates the instability. This torque
across the fracture site leads to additional displacement of the
bone segments 1,2 and shortening of the bone.
[0005] A conventional arrangement of treating oblique fractures of
the lateral malleolus of the ankle is illustrated in FIG. 2 which
comprises inserting two interfragmentary screws or pins 5 across
the fracture site. The interfragmentary screws 5 produce simple
side to side compression of the oblique fracture surfaces. Because
the fracture is oblique and the screws 5 only have a single point
of fixation 6 on each side of the fracture surface of fracture 3,
the screws 5 rely only on frictional forces across the fracture
site to prevent sliding of the oblique surfaces and resultant
shortening. Often such interfragmentary screws 5 cannot be placed
perpendicular to the plane of the fracture, which results in a
contribution of a force component that adds shear to the fracture
site. This is similar to the way a wedge will tend to slip out of a
vise as the vise is tightened.
[0006] Furthermore, since interfragmentary fixation relies on a
single point of contact of the screw within each bone fragment 1,2,
there is poor resistance to angular displacements and loss of
reduction with axial loading of the bone as shown in FIG. 3.
[0007] Even if the screws 5 can be placed perpendicular to the
fracture, this manner of fixation is not optimal since the bone is
often osteoporotic with the result that the threads of the screws
strip and lose purchase as compression is applied.
[0008] In addition, placing relatively large diameter holes in a
small bone fragment can result in further fracture propagation
through the screw hole. These factors limit the amount of
compression that can be achieved by simple interfragmentary bone
screw 5.
[0009] Fixation with interfragmentary screws is based entirely on
the use of one or two screws. The holding power of the screws is
based entirely on the purchase of the screw threads in the thin
cortex of the bone fragments 1,2, which is often tenuous. In
addition, this type of fixation is extremely weak in resisting
external rotational torque T on the ankle, which can also lead to
failure of fixation and a poor clinical result.
[0010] Another traditional means for fixation of oblique fractures
is shown in FIG. 4 in which a bone plate 7 is utilized. Such a bone
plate is used to statically hold the fragments 1, 2 in position
without any compression (so called neutralization plates) or to
hold the bone and create compression along the long axis of the
bone (so called compression plates). Neutralization plates do not
produce compression at the fracture site but instead depend
entirely on the purchase of bone screw 8 on either side of the
fracture and the strength of the plate. Fixation is along a single
axis and in one plane and is relatively weak in resisting torsional
loads. In addition, this type of fixation requires bulky plates and
a multitude of screws with larger surgical incisions.
Neutralization plates do not provide any load across the fracture
site, and may result in longer healing times as well.
[0011] Compression plates which produce compression along the axis
of the bone are effective for stable fixation of simple fractures
that are transverse (not oblique) to the long axis of the bone.
However, using a compression plate in the context of a long oblique
fracture produces shear forces at the fracture site as previously
described, resulting in sliding of the bone fragments with
shortening and loss of reduction. In addition, since the plate is
situated predominantly within a single plane, like neutralization
plates, they provide only a single plane of fixation with limited
ability to control rotational forces.
[0012] Recently, a plate for distal radius fractures has been used
in which there is a small tab extending from a distal edge of the
plate to act as a gutter to catch an edge of the bone. However,
this tab is designed as a positional reference for the plate to the
edge of the bone and is positioned at the extreme distal edge of
the plate. Because it does not extend deeply, rotation of the plate
would not produce any translational force to the bone, but rather
would cause the bone to slip out from under the tab. In addition,
the extreme distal nature of the position of this tab would cause
the distal fragment to rotate off the corner of the plate.
[0013] Another technique for fixation of long bone fractures is the
use of intramedullary pinning or rodding. Intramedullary fixation
is not effective for short oblique fractures as it provides no
rotational control and allows shortening of the bone.
SUMMARY OF THE INVENTION
[0014] An object of the invention is to provide a method and
apparatus for fixation of a fracture using an implant that produces
compressive load (oblique or perpendicular) to the long axis of the
implant across an oblique fracture line in order to facilitate
healing and avoid further shortening of the two bone fragments.
[0015] A further object of the invention is to provide such
fixation in which a counter-rotational torque is generated to
prevent sliding of the fragments and production of a destabilizing
force couple.
[0016] A further object of the invention is to provide a device
that is simple to apply, reduces the risk of iatrogenic comminution
from screw holes near the fracture site, allows improved resistance
to rotational torque, and avoids shortening at the fracture
site.
[0017] A further object of the invention is to provide a device
that provides multiple planes of fixation and is effective in
resisting shortening, shearing, and rotation at the fracture
site.
[0018] In accordance with the invention, a fracture fixation device
is provided which comprises a fixation plate, having tabs that
extend out of the plane of the plate on opposite edges; the tabs
extend a sufficient distance and are sufficiently rigid such that
the tabs contact the bone above and below the fracture line to
apply compressive forces to the bone in a transverse direction
(i.e. oblique or perpendicular to the long axis of the plate) in
order to develop compression of the bone fragment along the
fracture line.
[0019] In a further accordance with the invention, the tabs are
situated such that rotation of the plate causes the tabs to apply
compression forces on the bone fragments on either side of the
fracture while at the same time limiting shortening of the bone
across the fracture site, effectively producing a counter
rotational torque at the oblique fracture site and multiple plane
fixation of the bone fragments.
[0020] According to a feature of the invention, an instrument such
as a bending tool is used to enable the surgeon to further bend the
tabs against the bone both to customize the degree of contact as
well as to augment compression at the fracture site. In this way,
the tabs serve as a means for controlling the intensity of the
compressive force at the fracture site.
[0021] According to a further feature of the invention, the tabs
are shaped with stress relief notches or holes to direct bending of
the tab to a particular location.
[0022] According to a further feature of the invention, the tabs
are configured to have projections to dig into the surface of the
bone and improve fixation of the bone by the tabs.
[0023] In another feature of the invention, the tabs are provided
with holes or key-ways to allow the bending tool to lock into the
plate during bending of the tabs.
[0024] According to another feature of the invention, the tabs are
longitudinally offset to provide contact with the opposite bone
surfaces in an offset position, in order to compensate for an
oblique fracture as well as to increase the lever arm for increased
counter-rotational torque.
[0025] According to another feature of the invention, the tabs
extend a sufficient distance away from the edge of the plate to
prevent the engaged fragment from rotating off the edge of the
plate as compression is applied.
[0026] According to another feature of the invention, the tabs
allow placement of a screw, peg or wire to augment fixation by the
tabs along an axis that is out of the plane of the plate; in one
embodiment, this fixation element is threaded into the tab to lock
it therein; in another embodiment, a single screw, peg, wire or
bolt is passed from one tab oblique to the other and secured by
threading in the tab, locking it with a nut, or crimping it into
the tab.
[0027] According to another feature of the invention, one or more
of the bone screw holes in the plate is oblong, to allow sliding of
the plate along the bone on a partially inserted screw in order to
fine tune the position of the bone fragments before fixation; in
one embodiment, this oblong hole is oriented oblique to the
longitudinal axis of the plate, so that as the plate is slid along
the partially inserted screw, the oblique orientation of the hole
causes the plate to rotate, with the result that the tab is
compressed against the surface of the bone.
[0028] According to another feature of the invention, the plate is
curved along its long axis to conform with the curvature of the
bone, with or without a second curvature across the width of the
plate, in order to allow more intimate apposition to the bone, e.g.
the lateral malleolus of the ankle.
[0029] The invention also provides a method of fixation of an
oblique fracture of a bone, such as the lateral malleolus of an
ankle, which comprises the steps of:
[0030] reducing the fracture by abutting proximal and distal
fragments along the oblique fracture
[0031] applying a fixation plate along the fractured bone and
across the fracture such that a first portion of the fixation plate
is adjacent to the distal fragment and a second portion of the
fixation plate is adjacent to the proximal fragment,
[0032] providing tabs extending from the first and second portions
of the fixation plate at locations spaced longitudinally of the
plate and at positions at which one tab faces an upper surface of
the bone while another tab faces a lower surface of the bone,
and
[0033] bringing the tabs into contact with the upper and lower
surfaces of the bone to apply force to the distal and proximal
fragments of the bone and produce compression of the distal and
proximal fragments across the fracture.
[0034] Instead of providing tabs at the first and second portionso
f the fixation plate, a tab can be provided at only one portion of
the fixation plate. In such case, the tab is sufficiently long and
rigid to engage and apply transverse force to the bone such that
after the other portion of the fixation plate is secured to the
other bone fragment by bone screws, the tab can be brought into
contact with the surface of the bone to produce the transverse
force on the bone and the compression of the bone fragments along
the oblique fracture line.
BRIEF DESCRIPTION OF THE FIGURES OF THE DRAWING
[0035] FIG. 1 is a side view illustrating a conventional oblique
fracture of a bone in which the bone fragments have been
displaced.
[0036] FIG. 2 illustrates a conventional arrangement for fixation
of an oblique fracture.
[0037] FIG. 3 shows the arrangement of FIG. 2 in which the
fragments are displaced by application of a torque at the
fracture.
[0038] FIG. 4 illustrates another conventional arrangement for
fixation of the fracture.
[0039] FIG. 5 is a side elevational view of the fixation device
according to the invention installed on a bone having an oblique
fracture.
[0040] FIG. 6 is a top view of FIG. 5.
[0041] FIG. 7 is a sectional view taken on line 7-7 in FIG. 6.
[0042] FIG. 8. is an end view seen from the right end of FIG.
5.
[0043] FIG. 9 is an explanatory view showing the forces acting on
the bone with reference to the fixation device of FIG. 6.
[0044] FIG. 10 is a view similar to FIG. 6 showing a modification
of the fixation plate.
[0045] FIG. 11 is a side view of FIG. 10.
[0046] FIG. 12 is an end view from the right end of FIG. 10.
DETAILED DESCRIPTION
[0047] Referring to FIGS. 5 and 6, therein is shown distal and
proximal bone segments or fragments 10, 11 on opposite sides of an
oblique fracture 13 of the lateral malleolus bone 14 of the ankle.
Although the invention will be described with reference to the
lateral malleolus, it is applicable to oblique fractures of other
long bones such as the ulna, humerus, tibia, femur etc.
[0048] Attached to the side of the bone 14 is a fixation plate 15
of a fixation implant for fixation of the fracture 13. The fixation
plate 15 has a distal portion 16 adapted for being secured by bone
screws 17 to the distal fragment 10 and a proximal portion 18
adapted to be secured to the proximal fragment 11 by bone screws
19.
[0049] The fixation plate 15 is made of surgical material such as
titanium or stainless steel. Its length and thickness is a function
of the bone which is fractured. In a typical case of the lateral
malleolus, the thickness of plate 15 will be between 0.025'' and
0.375'' and its length will be between 0.5'' and 5.0''. For
fractures of other bones, the dimensions of the fixation plate will
be determined by the surgeon as is well known in the art. The
fixation plate is required to have sufficient rigidity to secure
the fragments in a stable position.
[0050] At the upper edge of proximal portion 18, a tab 20 extends
outwards of the fixation plate 15 and at the lower edge of the
distal position 16, a tab 21 extends outwards of the fixation plate
15 in the same direction as tab 20. The tabs 20 and 21 are
longitudinally spaced from one another (by a distance d as shown in
FIG. 9) and are disposed on opposite sides of the fracture 13 such
that tab 20 is disposed above the fracture 13 whereas tab 21 is
disposed below the fracture 13.
[0051] As seen in FIGS. 7 and 8, tab 20 has an extending leg
portion 22 which extends around the upper surface of the proximal
fragment 11. The leg portion 22 has a lower end 23 with a pointed
tip 24 forming a tooth.
[0052] Tab 21 is a mirror image of tab 20 and has the same shape as
tab 20 and leg portion 25 and pointed tip 26.
[0053] The tabs 20 and 21 are intended to be bent against the
respective bone fragments. The teeth of pointed tips 24 and 26 then
bite into the respective bone fragments to secure the tabs to the
bone fragments. A bending tool (not shown) is utilized to bend the
tabs 20, 21 and apply the compressive force against the bone
fragments. For smaller fragments, the tabs may be manually bendable
by the surgeon to press tabs against the bone fragments and cause
the teeth of the tabs to bite into the fragments. In any event, the
tabs 20, 21 have sufficient length to extend over the surfaces of
the bone fragments and the tabs are suitably rigid to provide
adequate strength to apply the transverse forces to the bone
fragments. The tabs can have the same thickness as the plate.
[0054] The tabs can also be secured together by a pin 30, which
extends in the distal and proximal fragments and across the
fracture as shown in FIGS. 5 and 6. The pin 30 is installed in the
tabs 20, 21 and the ends of the pins are then bent back against the
tabs. The pin 30 provides a further degree of stabilization of the
fracture.
[0055] The tabs 20, 21 can be initially in the plane of the plate
and bent outwardly of the plate either manually or by the bending
tool to extend adjacent to the surface of the bone fragments.
[0056] The tabs may be provided with holes 27 to receive the
bending tool and enable the bending of the tabs.
[0057] The tabs may be provided with stress relief holes or notches
32 to direct the line of bending of the tabs in a particular
direction.
[0058] The tabs can apply the compressive force to the fragments
directly. Alternatively and, particularly for larger plates, after
the tabs have been bent to face the bone fragments, screws or pins
28 can be used to develop the compressive force against the bone
such as by providing the holes 27 with threads and thread ably
advancing the screw or pins 33 in the holes. The screws or pins 33
can also provide an additional means to secure the tabs to the
fragments by advancing into the bone.
[0059] FIG. 9 is an explanatory view showing the forces F1, F2
applied by the tabs 20, 21 against the bone fragments.
[0060] The forces F1 and F2 are transverse to the bone and have
components which apply compressive force across the oblique
fracture 13. Because forces F1 and F2 are longitudinally spaced by
a distance d along the longitudinal axis of the bone, they produce
a force couple or torque T opposing displacement of the bone
fragments (sliding along the fracture line) which would produce
bone shortening. The tabs 20, 21 also provide a counter-rotational
torque to oppose rotation of the fracture site which would produce
shortening of the bone. After the tabs 20, 21 have been bent
against the bone fragments and before bone screws 17 or 19 have
been inserted, the fixation plate can be rotated clockwise or
counter clockwise respectively to increase or decrease the
compressive pressure of the tabs against the bone fragments to
adjust the compression of the bone fragments across the
fracture.
[0061] Although two tabs 20, 21 have been shown in the drawings, it
is also possible to employ only one tab (20 or 21) to achieve the
compression across the fracture and the counter-resisting torque.
Thus, for example, if only tab 20 is provided, it can apply force
F1. The attachment of plate 15 by screws 17 to the distal fragment
will provide opposed resistance corresponding to force F2 to
achieve the compression across the fracture and the
counter-resistant torque when force F1 is applied by tab 20.
Preferably, however, tabs 20, 21 are provided on opposite sides of
the plate as this permits greater control of the applied transverse
forces. Additionally, more than one tab can be provided on the
opposite sides of the plate to distribute the transverse forces
over a greater length.
[0062] To facilitate the adjustment of the compression across the
fracture, one of the holes in the proximal portion 18 for receiving
a bone screw 19 is formed as an oblong hole 28 tilted upwardly in
FIG. 10 in the direction from the distal portion 16 to the proximal
position 18. Thus, if the proximal fragment is displaced in a
direction away from the distal fragment, the fixation plate 15 will
be urged to rotate clockwise, pressing the tab 20 against the
proximal fragment and the tab 21 against the distal fragment with
increasing force to increase the compression across the fracture.
Movement in the opposite direction will relieve the compression.
The oblong hole 28 also serves the function of fine tuning the
installation of the plate. In this regard, the bone screw is
loosely placed in the center of the oblong hole 28 to allow sliding
of the plate along the screw which causes the plate to rotate and
produce varied compression force applied by the tabs against the
bone fragments.
[0063] The plate 15 is shaped to accommodate itself to the
particular bone being treated, e.g. the lateral malleolus of the
ankle. Thus, as seen in FIG. 6, the plate 15 is outwardly curved at
its forward end adjacent to the distal fragment and then the plate
follows the configuration of the bone as the plate extends
rearwardly. In the transverse or cross-sectional direction, the
plate is curved or bent outwardly as shown in FIG. 8 to extend over
and around the lateral surface of the bone.
[0064] In a modification as shown in FIGS. 11-12, the forward end
of the plate is extended and is provided with a downwardly bent lip
29 for engaging the distal surface of the distal fragment 10 so
that pressure can be applied by the lip to the distal fragment in a
direction to apply compression force at the fracture site. The
lower end of the lip can be provided with teeth to bite into the
distal fragment to secure the lip to the fragment.
[0065] Although the invention has been described with reference to
specific embodiments, it will be apparent to those skilled in the
art that numerous modifications and variations can be made within
the scope and spirit of the invention as defined in the attached
claims.
* * * * *